The use of packet-based communication in the home has increased dramatically in the last few years and is poised to explode in the near future. The medium for connecting devices in the home network is varied. It ranges from dedicated wired, to wireless, phone lines and recently also power lines connections. Currently, the main application of networks in the home are to connect computers and share Internet connections, but other applications loom on the horizon. One of the prominent candidates for home LAN applications is audio and video distribution. Synchronization of the different components is very important in making these applications viable. An advanced audio system, for example, may be composed of several speakers spatially separated from each other and interconnected with a LAN. To maintain a high fidelity, it is important that all the audio streams are synchronized to within about 10-20 milliseconds. Larger delays will be perceptible and will negatively impact the listening experience.
Another related problem that tends to occur when using today's digital music is the phenomenon of time drift. To illustrate the problem, assume that synchronization is achieved between the remote speakers at a certain point in time. Furthermore, assume that the long-term clock accuracy of the network element's crystal oscillator is on the order of 50*10−6. (Better accuracy is achievable, but at a price). The music on one device will run faster (or slower) than on the other devices. This time-drift from the point in time where the two devices are synchronized is readily calculated to yield (approximately):D=I*T  (Eq. 1)where D is the time drift, T is the time lapsed from the point of synchronization, and I is the frequency inaccuracy.
So, for example, after 5 minutes of play time (from synchronization) the drift between two speakers becomes:D=100*10−6*300=30 Milliseconds  (Eq. 2)
Clearly, this is not tolerable. Thus, it would be very beneficial if a practical solution to the above problem would be found.